1. Field of the Invention
The invention generally relates to force measurement systems. More particularly, the invention relates to a force measurement system that comprises a plurality of force measurement assemblies configured to be displaced around a continuous path of movement.
2. Background and Description of Related Art
Force measurement systems are utilized in various fields to quantify the reaction forces and moments exchanged between a body and support surface. For example, in biomedical applications, force measurement systems are used for gait analysis, assessing balance and mobility, evaluating sports performance, and assessing ergonomics. In order to quantify the forces and moments resulting from the body disposed thereon, the force measurement system includes some type of force measurement device. Depending on the particular application, the force measurement device may take the form of a balance plate, force plate, jump plate, an instrumented treadmill, or some other device that is capable of quantifying the forces and moments exchanged between the body and the support surface.
Conventional force measurement systems have numerous limitations and drawbacks. For example, conventional force measurement systems comprising typical force plates are stationary, and thus do not easily accommodate a subject walking or running thereon. To overcome this limitation, a large array of adjacent stationary force plates may be provided. However, force plate arrays occupy a large amount of valuable building floor space, which could be used for other purposes. Instrumented treadmills are an alternative to force plate arrays. Although, instrumented treadmills have their own limitations and drawbacks. First of all, dual-belt instrumented treadmills are subject to leg crossing problems. Each of the belts of a dual-belt treadmill is designed to accommodate a single respective one of the subject's legs. However, during normal walking or running on an instrumented treadmill, subjects often cross their legs such that, for example, the right foot of the subject contacts the left belt of the instrumented treadmill and/or the left foot of the subject contacts the right belt of the instrumented treadmill. This leg crossing problem results in the acquisition of inaccurate gait data by the instrumented treadmill, which must be discarded. The test must then be repeated on the instrumented treadmill in order to acquire accurate gait data. In order to avoid the leg crossing problem, subjects sometimes modify their gait while walking or running on the instrumented treadmill, but this is not an appropriate remedy for the leg crossing problem because the self-imposed gait modifications result in an artificial gait data that does not reflect a subject's typical walking or running style.
Another limitation of conventional force measurement systems in the form of instrumented treadmills is associated with those systems that employ two separate belts (one behind the other) in the walking or running direction of the subject. In these systems, there is a transversely extending seam between the anterior and posterior belts that subject's feet often contact. Even if the width of this belt seam is greatly minimized, this belt seam can still interfere with the subject's normal gait pattern.
Therefore, what is needed is a force measurement system that employs a compact arrangement of force plates that is capable of accurately assessing the gait of a subject when the subject walks or runs on the force measurement system. Moreover, what is needed is a force measurement system that does not have the leg crossing problems associated with dual-belt instrumented treadmills. Furthermore, a force measurement system is needed that does not have the belt seam problems that are associated with instrumented treadmills having posteriorly and anteriorly located belts.